An effective HIV vaccine should induce in a diverse human population broadly-neutralizing anti-HIV antibodies [bnHIV-Ab] that target most or all HIV subtypes. Although inducing neutralizing antibodies against HIV by vaccination has proven to be a challenge, individuals with autoimmune disease frequently make polyreactive antibodies that also neutralize HIV infection. The long-term goal for the research proposed is to develop strategies that lead to induction of broadly reactive neutralizing antibodies that can prevent infection by a wide variety of clinically relevant strains. The hypothesis is that adolescents with autoimmunity with or without concurrent HIV infection are likely to harbor unique peripheral B cells that produce polyreactive antibodies with long and hydrophobic VH CDR3 regions, which are characteristics of known bnHIV-ab. The strategy to accomplish the research goals uses the exploratory/developmental R21 mechanism and an interdisciplinary approach to apply high impact basic immunology studies and innovative methods to explore the depth of the B-cell repertoire, to increase the panel of broadly neutralizing HIV-1 antibodies available by creating a novel phage display library, and to identify the B cell subset[s] that produce these antibodies. The study population includes a unique group of HIV infected adolescents with autoimmunity, as well as individuals with autoimmunity or HIV infection. Two related Specific Aims are proposed: 1. to search for specific B cell types producing broad reactive neutralizing antibodies with long VH CDR3;and 2. to develop and characterize broadly-neutralizing HIV antibodies. Specific Aim 1 will characterize peripheral blood B cell populations by multi-color flow cytometry, examine the depth of IgG and IgM antibody repertoires in subjects by high-throughput 454 Life Science pyrosequencing of VH CDR3 domains, and determine the localization of long, hydrophobic VH CDR3 domains within subsets of B cells. Specific Aim 2 combines the power of antibody phage display with autoimmune individuals, who are enriched for B cells that produced polyreactive autoantibodies, to develop a custom library that will be screened against a complex mixture of virion subtypes to isolate bnHIV-Ab. The proposed research will provide significant fundamental information about cellular aspects of human immunity and the molecular diversity of the antibody repertoire, and result in generation of broadly neutralizing HIV antibodies with novel specificities and/or biochemical characteristics. HIV/AIDS is a global pandemic for which there is currently no vaccine and no cure. Although inducing neutralizing antibodies against HIV by vaccination has proven to be a significant challenge, individuals with autoimmune disease frequently make antibodies that also neutralize HIV infection. The exploratory/developmental research proposed will apply state-of-the-art technology for a comprehensive cellular and molecular analysis of HIV-specific antibody responses in autoimmune individuals. The results will provide major advancements in understanding the immune response to HIV and will form a basis for developing novel vaccine strategies to induce an effective anti-HIV response.